Studies on mechanism of thyroxine action on gene repression and derepression in amphibian metamorphosis of tadpole; this includes acetylation and methylation of nuclear proteins (histone and nuclear acidic proteins) in vivo and in vitro during thyroxine-induced tadpole metamorphosis. Effect of various enzymes in modifying the amino acid side chains (Protein methylase I, II, III, epsilon-lysine acylase, epsilon- alkyllysinase, epsilon-N-acetyllysine synthetase as well as histone hydrolase). Studies on the enzymatically altered protein for changes in structure and function.